IS-05-02 test_15 cannot handle an fmtp attribute with channel-order=SMPTE2110.(AES3)

[billt-hlit]

This problem opens a can of worms, I fear. SMPTE ST 2110-31:2018 defines "AES3" as a new grouping symbol. However, unlike 2110-30, it does not define the order of the channels in the AES3 group, so it's not clear what symbols should be used in the channels array for the Source corresponding to the Sender using AES3 as its channel order in its transportfile.

[jonvmey]

Somewhat related, I imagine that test would also have problems with 2110-30's "SGRP" and "222" grouping symbols since IS-04 Sources can't represent those either.